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Generation of Suprathermal Electrons by Collective Processes in Collisional Plasma
- Source :
- Published 2017 November 8, copyright 2017. The American Astronomical Society. All rights reserved
- Publication Year :
- 2017
-
Abstract
- The ubiquity of high-energy tails in the charged particle velocity distribution functions observed in space plasmas suggests the existence of an underlying process responsible for taking a fraction of the charged particle population out of thermal equilibrium and redistributing it to suprathermal velocity and energy ranges. The present Letter focuses on a new and fundamental physical explanation for the origin of suprathermal electron distribution function in a highly collisional plasma. This process involves a newly discovered electrostatic bremsstrahlung emission that is effective in a plasma in which binary collisions are present. The steady-state electron velocity distribution function dictated by such a process corresponds to a Maxwellian core plus a quasi-inverse power-law tail, which is a feature commonly observed in many space plasma environment. In order to demonstrate this, the system of self-consistent particle- and wave- kinetic equations are numerically solved with an initially Maxwellian electron velocity distribution and Langmuir wave spectral intensity, which is a state that does not reflect the presence of electrostatic bremsstrahlung process, and hence not in force balance. The electrostatic bremsstrahlung term subsequently drives the system to a new force-balanced steady state. After a long integration period it is demonstrated the initial Langmuir fluctuation spectrum is modified, which in turn distorts the initial Maxwellian electron distribution into a velocity distribution that resembles the said core-suprathermal velocity distribution. Such a mechanism may thus be operative at the coronal source region, which is characterized by high collisionality.<br />Comment: 7 pages, 2 figures. Published at: The Astrophysical Journal Letters, Volume 849, Number 2, L30. url: https://doi.org/10.3847/2041-8213/aa956f
- Subjects :
- Physics - Plasma Physics
Physics - Space Physics
Subjects
Details
- Database :
- arXiv
- Journal :
- Published 2017 November 8, copyright 2017. The American Astronomical Society. All rights reserved
- Publication Type :
- Report
- Accession number :
- edsarx.1708.05780
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.3847/2041-8213/aa956f